Any size and location of concatenated packet data across SONET frames in a SONET signal

ABSTRACT

A method and apparatus for the incorporation of any size and location of concatenated SONET frames, which carry packet data, in an SONET signal are described. In an embodiment, a method includes receiving packet data. Additionally, the method includes concatenating the packet data into a Time Division Multiplexing (TDM) Synchronous Optical Network (SONET) signal. The concatenation can be across any locations within the TDM SONET signal, and a size of the concatenation can be in increments of single SONET frames. The method also includes transmitting the TDM SONET signal having the concatenated packet data.

FIELD OF THE INVENTION

The invention relates to the field of telecommunications. Morespecifically, the invention relates to network elements in SynchronousOptical Network (SONET) standard and/or Synchronous Digital Hierarchy(SDH)-based telecommunication networks that allow for any size andlocation of concatenated Synchronous Transport Signal (STS) frameshaving packet data in a SONET/SDH signal.

BACKGROUND OF THE INVENTION

With the advent of the Internet and the World Wide Web (WWW), the needfor high-speed transmission of data including video and audio hascontinued to increase. Moreover, in addition to the demand for higherbandwidth, there has also been an increased need for various types ofservices that employ different protocols. For example, certain customers(e.g., companies providing voice services) of high-speed networks wantto operate on a Time Division Multiplexing (TDM) Network, which combinesdifferent data streams such that each data stream is assigned a timeslot within the combined data stream. Moreover, other customers ofhigh-speed networks may desire to transport data employing packet-baseddata streams, which do not have dedicated timeslots to given packets.Examples of the types of packets that can be placed into such datastreams can include Asynchronous Transfer Mode (ATM), Internet Protocol(IP), Frame Relay, voice over IP and Point-to-Point Protocol (PPP).

Typically, Time Division Multiplexing (TDM)-based SONET and SDHtechnologies can transport this packet data traffic in today's market.While traditional TDM networks can currently carrying this packet datatraffic, such networks are inefficient in their usage of bandwidth. Inparticular, TDM networks reserve different portions of bandwidth forusage by given customers, independent of whether such customers aretransporting data traffic on that bandwidth. Moreover, the servicedeployment of such networks remains slow. As a result, there is amigration away from TDM networks toward a packet-based network, which ismore dynamic in nature. In particular, a packet-based network onlyemploys the portion of the bandwidth needed for its transmission. Inother words, there are no fixed time slots in a packet-based network.However, TDM networks still have a place in the telecommunicationsnetwork, as certain customers may demand the reservation of portions ofbandwidth within the network, regardless of their usage of thisbandwidth. Therefore, both TDM-based and packet-based networking arestill needed in the field of telecommunications. Additionally, TDMsignals and packet data are not mutually exclusive, as TDM signals cantransport packets.

Disadvantageously, advantages gained through the use of packets are lostwhen such packets are placed into a TDM network. In particular, fixedtime slots are reserved for the transporting of these packets on such anetwork. As a result, there is a need for network elements with thedynamic capability of adjusting to meet the different needs ofcustomers, including those desiring a TDM data stream as well as thosewanting a more efficient usage through networks employing packetstreams.

SUMMARY OF THE INVENTION

A method and apparatus for the incorporation of any size and location ofconcatenated SONET frames, which carry packet data, in an SONET signalare described. In an embodiment, a method includes receiving a number ofpackets. Additionally, the method includes concatenating the number ofpackets into a Time Division Multiplexing (TDM) Synchronous OpticalNetwork (SONET) signal. The concatenation can be across any locationswithin the TDM SONET signal, and a size of the concatenation can be inincrements of single SONET frames. The method also includes transmittingthe TDM SONET signal having the number of concatenated packets.

In one embodiment, a method includes receiving a number of packetswithin a first Time Division Multiplexing (TDM) Synchronous OpticalNetwork (SONET) signal having a number of SONET frames. The number ofpackets is concatenated across any of the number of SONET frames withinthe first TDM SONET signal. Additionally, a size of the concatenationcan be in increments of single SONET frames. Upon determining that thenumber of packets is being transmitted to a first location that cannotextract the number of packets from any of the number of SONET frames inthe first TDM SONET signal, the method also includes extracting thenumber of packets from the first TDM SONET signal. Additionally, anumber of SONET frames in a second TDM SONET signal are filled withtransmission data that includes the number of packets. The filling isequally interleaved across the number of SONET frames in the second TDMSONET signal. Moreover, upon determining that the number of packets isbeing transmitted to the first location, the method also includestransmitting the second TDM SONET signal to the first location. Upondetermining that the number of packets is being transmitted to a secondlocation that can extract the number of packets from any of the numberof SONET frames in the first TDM SONET signal, the method includestransmitting the first TDM SONET signal to the second location.

In an embodiment, a network element of a network ring includes physicalconnection circuitry having a number of buffers. The number of buffersholds packet data received from a different network element that isexternal to the network ring. Additionally, the physical connectioncircuitry determines packet boundaries for the packet data. The networkelement also includes packet processing circuitry coupled to thephysical connection circuitry. The packet processing circuitry receivesthe packets from the physical connection circuitry and concatenates thepackets into any location with a Time Division Multiplexing (TDM)Synchronous Optical Network (SONET) signal.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention may be best understood by referring to thefollowing description and accompanying drawings which illustrate suchembodiments. The numbering scheme for the Figures included herein aresuch that the leading number for a given element in a Figure isassociated with the number of the Figure. For example, system 100 can belocated in FIG. 1. However, element numbers are the same for thoseelements that are the same across different Figures. In the drawings:

FIG. 1 is block diagram illustrating a system that incorporatesembodiments of the present invention;

FIG. 2 illustrates portions of in-ring network elements 102-108,according to embodiments of the present invention;

FIG. 3 illustrates a block diagram of the relationship between twoin-ring network elements for the transmission of packet traffic withinnetwork ring 114, according to embodiments of the present invention;

FIG. 4 illustrates a block diagram of the relationship among at leastthree in-ring network elements for the transmission of packet trafficwithin network ring 114, according to embodiments of the presentinvention;

FIG. 5 illustrates a more detailed diagram of portions of a line cardwithin a network element, according to embodiments of the presentinvention; and

FIG. 6 is a block diagram of a SONET signal carrying both TDM data andIP packets, according to embodiments of the present invention.

DETAILED DESCRIPTION

A method and apparatus for the incorporation of any size and location ofconcatenated SONET frames, which carry packet data, in an SONET signalare described. Embodiments of the present invention are described hereinin terms of a SONET signal. However, embodiments of the presentinvention are not so limited, as such embodiment can be employed usingthe SDH signal. Moreover, a SONET standard is referred to herein, whichis currently defined by Bellcore GR-253. Additionally, in the followingdescription, for purposes of explanation, numerous specific details areset forth in order to provide a thorough understanding of the presentinvention. It will be evident, however, to one skilled in the art thatthe present invention may be practiced without these specific details.

System Description

FIG. 1 is block diagram illustrating a system that incorporatesembodiments of the present invention. In particular, FIG. 1 illustratessystem 100 that includes network ring 114, which is comprised of in-ringnetwork element 102, in-ring network element 104, in-ring networkelement 106 and in-ring network element 108. System 100 also includenon-ring network element 110, non-ring element 111 and non-ring networkelement 112, which are coupled to network ring 114 through in-ringnetwork element 102, in-ring network element 104 and in-ring networkelement 106, respectively. In an embodiment, non-ring elements 110-112can be routers, switches, bridges or other types of network element thatswitch data across a network.

In one embodiment, the connection among in-ring network element 102,in-ring network element 104, in-ring network element 106 and in-ringnetwork element 108 allow for bi-directional traffic. Accordingly, thisbi-directional capability allows for redundancy in the communicationbetween the different network elements, such that if a given line ofcommunication is lost, the data traffic to be transmitted thereon can bererouted in the opposite direction to reach its intended destinationwithin the ring architecture.

In an embodiment, system 100 transmits data traffic among the differentnetwork elements, both in-ring and non-ring, employing the SynchronousOptical Network (SONET) standard or Synchronous Digital Hierarchy (SDH).However, embodiments of the present invention are not so limited, asdata traffic among the different network elements can be transferredusing other types of transmission standards. Examples of other types oftransmission standards can include, but are not limited to, T1, T3, DataSignal (DS)3 and DS1 signals. In one embodiment, data traffic amongin-ring network element 102, in-ring network element 104, in-ringnetwork element 106 and in-ring network element 108 includes TDM trafficand packet traffic within a same Time Division Multiplexing (TDM)signal.

In this ring network, network elements are used that can transmit andreceive TDM ring traffic. In addition, at least certain of the networkelements provide two different switching techniques—TDM and packet. Thepacket switching provided can support any number of protocols includinglayer 2 and layer 3 type protocols such as ATM, Ethernet, Frame Relay,etc. In addition to typical operations of a TDM network element, thenetwork elements are implemented to be able to: 1) programmably selecton an STS basis certain of the incoming TDM traffic to be extracted andpacket switched rather than TDM switched; and/or 2) receive packettraffic in another form and to be packet switched. Regardless of whichswitching technique is used, the switched traffic going back onto thering is put in TDM format and transmitted out. However, each timetraffic is packet switched, that traffic can be statisticallymultiplexed (e.g., the packets can be selectively dropped based onvarious criteria). A further description of the operation of system 100and the network elements therein is described in more detail below.

The architecture and configuration of system 100 is by way of exampleand not by way of limitation, as embodiments of the present inventioncan be incorporated in other types of systems. For example, other suchsystems could incorporate less or more network elements into the networkring and/or network elements attached thereto. Moreover, embodiments ofthe present invention are not limited to the network ring architectureas illustrated in FIG. 1. Examples of other types of networkarchitectures that can incorporate embodiments of the present inventioninclude, but are not limited to, a point-to-point configuration,point-to-multipoint configuration and/or a hub configuration. Inaddition, embodiments of the present invention are not limited to TDMnetworks, but also applies to Wave Division Multiplexing (WDM) networks.

Network Element Description

FIG. 2 illustrates portions of in-ring network elements 102-108 (forpurposes of FIG. 2, hereinafter “network element 102”), according toembodiments of the present invention. As shown, network element 102includes line cards 202 a-d and control card(s) 220, such that controlcard(s) 220 are coupled to each of line cards 202 a-d. The number ofline cards illustrated are for the sake of simplicity and not by way oflimitation, as a lesser or greater number of line cards can be includedwithin network element 102. Additionally, network element 102 includes afirst switch fabric, packet mesh 226, which includes a full mesh suchthat each of line cards 202 a-d are coupled to one another. For example,line card 202 a is coupled to line cards 202 b-d through packet mesh226. However, embodiments of the present invention are not limited to afull mesh for the transmission of packets among line cards 202 a-d, asany type of switching method that switches based on the addressingscheme described herein can be incorporated into embodiments of thepresent invention. For example, in one embodiment, line cards 202 a-dcould be coupled together using a switch fabric, such that the linecards are coupled to a control card, which provides for the switchingtherein.

Line cards 202 a-d include physical connection circuitry 210 a-d,ingress packet processing circuitry 212 a-d and egress packet processing214 a-d, respectively. Physical connection circuitry 210 a-d can becoupled to lines external to network element 102, as shown, which cancarry optical and/or electrical signals, which is described in moredetail below in conjunction with FIG. 7. In one embodiment, line cards202 a-d of network element 102 may be connected to an optical linetransmitting SONET OC-N signals. Moreover, in an embodiment, line cards202 a-d of network element 102 may be connected to an electrical linesuch as a T1, T3, E1, E3, Ethernet, Gigabit Ethernet, etc. However,embodiments of the present invention are not limited to theabove-described examples, as any other type of optical or electricaldata transmission can be incorporated into embodiments of the presentinvention. Additionally, control cards(s) 220 include TDM switchingcircuitry 216.

In an embodiment, each line card 202 a-d can be coupled to four opticaland/or electrical lines. In another embodiment, each line card 202 a-dcan be coupled to eight optical and/or electrical lines. However,embodiments of the present invention are not so limited, as a lesser orgreater number of optical and/or electrical lines can be coupled tonetwork element 102 through line cards 202 a-d. Additionally, physicalconnection circuitry 210 a-d are coupled to ingress packet processingcircuitry 212 a-d, respectively, such that packet data being receivedfrom the optical and/or electrical lines is passed from physicalconnection circuitry 210 a-d to ingress packet processing circuitry 212a-d, respectively. In one embodiment, the packet data is extracted froma TDM signal, which is described in more detail below.

Ingress packet processing circuitry 212 a-d is coupled to packet mesh226. Accordingly, each ingress packet processing circuitry 212 a-d iscoupled to each egress packet processing circuitry 214 a-d,respectively, on other line cards 202 a-d through packet mesh 226.Moreover, egress packet processing circuitry 214 a-d is respectivelycoupled to physical connection circuitry 210 a-d, such that packet datatraffic coming in from packet mesh 226 from ingress packet processingcircuitry 212 a-d is transmitted from egress packet processing circuitry214 a-d to physical connection circuitry 210 a-d, respectively.

Line cards incorporated into embodiments of the present invention arenot limited to those illustrated by line cards 202 a-d. Moreover, thenetwork elements can have different line card configurations from thatshown by line cards 202 a-d. For example, a given in-ring networkelement could be limited to a single line card that can receive andtransmit TDM traffic (which may include packet traffic) within networkring 114, employing multiple interfaces for the receipt and transmittalof TDM traffic. In another embodiment, a given in-ring network elementcan include a first line card to receive TDM traffic (which may includepacket traffic) from another in-ring element, while a second line cardcan transmit TDM traffic to another or same in-ring network element. Inone such embodiment, a third line card can be incorporated into thisgiven in-ring network element to add, drop and transmit different typesof traffic including different types of packet traffic, such as ATM,Frame Relay, IP, etc, received and transmitted to a non-ring networkelement. In another embodiment, a given network element may include asingle line card with multiple interfaces such that a first interfacereceives TDM traffic from another in-ring network element, a secondinterface transmits TDM traffic to another in-ring network element and athird interface adds, drops and transmits traffic, such as packettraffic to a non-ring network element.

Accordingly, a line card is used either to connect to an in-ring networkelement to form part of the ring, or to provide communication without-of ring network elements. To provide some examples with regard to aline card connected with an out-of-ring network element: 1) layer 2/3traffic from out-of-ring network element can come in, go through thepacket mesh to a line card connected to an in-ring network element, andthen out onto the ring being carried by a SONET frame; 2) layer 2/3traffic coming from an out-of-ring network element can be de-mapped intoSONET, go through the TDM switch fabric to a line card connected to anin-ring network element, and then out onto the ring being carried by aSONET frame; 3) TDM traffic coming from an out-of-ring network elementcan come in, go through the TDM switch fabric to a line card connectedto an in-ring network element, and then out onto the ring being carriedby a SONET frame; 4) TDM traffic carrying layer 2/3 traffic can beprocessed to extract the layer 2/3 traffic, with the layer 2/3 trafficgoing through the packet mesh to a line card connected to an in-ringnetwork element, and then out onto the ring carried by a SONET frame;layer 2/3 traffic coming form an out-of-ring network element can gothrough the packet mesh to an line card connected to an out-of-ringnetwork element, and then go out of the ring being carried by theprotocol of the interface of that egress line card; etc.

With regard to the TDM traffic, a second switch fabric (in addition topacket mesh 226) is formed among line cards 202 a-d and TDM switchingcircuitry 216 of control cards 220, as illustrated by the dashed linesin FIG. 2. In particular, physical connection circuitry 210 a-d iscoupled to TDM switching circuitry 216 for the receiving andtransmitting of TDM traffic into and out of network element 102.Accordingly, TDM switching circuitry 216 receive TDM traffic fromphysical connection circuitry 210 a-d and switches this traffic to anyof physical connection circuitry 210 a-d, based on configuration datafor the timeslots of the TDM traffic. For example, TDM switchingcircuitry 216 could be configured such that data within the first tentimeslots of a TDM signal, such as a SONET/SDH signal, received on afirst interface of physical connection circuitry 210 a are forwarded outthe first five timeslots of a TDM signal being transmitted out from afirst interface of physical connection circuitry 210 d.

Operation of Network Elements in System Embodiments

FIGS. 3 and 4 illustrate block diagrams of the relationship between anumber of in-ring network elements for the transmission of packettraffic within network ring 114, according to embodiments of the presentinvention. FIG. 3 illustrates a block diagram of the relationshipbetween two in-ring network elements for the transmission of packettraffic within network ring 114, according to embodiments of the presentinvention. In particular, FIG. 3 illustrates the traversal through twoin-ring network elements prior to the transmission out from network ring114. Conversely, FIG. 4 illustrates a block diagram of the relationshipamong at least three in-ring network elements for the transmission ofpacket traffic within network ring 114, according to embodiments of thepresent invention.

To help illustrate, returning to system 100 of FIG. 1, FIG. 3illustrates an embodiment of the transporting of a packet from non-ringnetwork element 110 to in-ring network element 102 to in-ring networkelement 104 and out to non-ring network element 111. In contrast, FIG. 4illustrates an embodiment of the, transporting of a packet from non-ringnetwork element 110 to in-ring network element 102 to in-ring networkelement 104 to in-ring network element 106 and out to non-ring networkelement 112.

FIG. 3 and FIG. 4 include in-ring network element 102 and in-ringnetwork element 104. Additionally, in-ring network element 102 includesline cards 302-316 and control card(s) 340, while in-ring networkelement 104 includes line cards 318-332 and control card(s) 342. FIG. 4also includes in-ring network element 106 that includes line cards402-416 and control card(s) 450. Moreover, FIGS. 3 and 4 include thedata paths for a given packet being switched through network ring 114.However, for the sake of clarity, FIGS. 3 and 4 do not include thepacket meshes or the switch fabric that couple together the differentline cards and control cards within a given in-ring network element andthrough which the data path for the given packet is transmitted, asillustrated in FIG. 2. The operation of in-ring network elements 102-106and the transmission of the data packet illustrated in FIGS. 3 and 4 aredescribed in more detail below, subsequent to the description of FIGS. 5and 6.

FIG. 5 illustrates a more detailed diagram of portions of a line cardwithin a network element, according to embodiments of the presentinvention. In particular, FIG. 5 illustrates a more detailed diagram ofphysical connection circuitry 210, ingress packet processing circuitry212, egress packet processing circuitry 214 and the interfaces therebetween, according to embodiments of the present invention. As shown,physical connection circuitry 210 includes input buffers 502-508 andoutput buffers 510-516. In an embodiment, input buffers 502-508 andoutput buffers 510-516 can be different types of writeable/readablememory (e.g., RAM). In one such embodiment, input buffers 502-508 arewithin a same memory. Similarly, in an embodiment, output buffers510-516 are within a same memory. Additionally, because egress packetprocessing circuitry 214 is capable of receiving packet data frommultiple ingress packet processing circuitry 212 of other line cards,egress packet processing circuitry 214 also includes a memory (notshown) for buffering of such packet data during their transmission tooutput buffers 510-516, which is described in more detail below.

Input buffers 502-508 and output buffer buffers 510-516 are assigned toone to a number of Synchronous Transport Signal (STS) frames in theSONET signal transmitted inside and/or outside network ring 114. In anembodiment, this assigning (i.e., provisioning) occurs dynamicallythrough provisioning data transmitted from control cards 220. In onesuch embodiment, the number of STS frames to be concatenated for a givenbuffer can be of any size for the SONET signal being transmitted amongin-ring network elements 102-108. Moreover, in an embodiment, the STSframes that are concatenated can be located anywhere within the SONETsignal.

To help illustrate, FIG. 6 is a block diagram of a SONET signal carryingTDM and packet traffic, according to embodiments of the presentinvention. In particular, FIG. 6 illustrates a OC48 SONET signal, whichcould be transmitted among in-ring network elements 102-108. As shown,the 48 frames of this OC48 signal are apportioned into different groups.In particular, TDM traffic is located in OC1-9, OC12-21, OC24-35,OC38-44 and OC47-48 within SONET portion 602, 606, 610, 614 and 618,respectively. Accordingly, the SONET signal of FIG. 6 has OC8 worth ofunused bandwidth, thereby having holes at OC10-11, OC22-23, OC36-37 andOC45-46 therein. Therefore, packet traffic can be located within any ofsuch holes in the SONET signal. In particular, packet traffic can belocated in OC10-11, OC22-23, OC36-37 and OC45-46 within SONET portion604, 608, 612 and 616, respectively. Input buffers 502-508 can,therefore, be assigned to one or any number of these OC frames notoccupied by the TDM traffic. For example, in one embodiment, inputbuffer 502, input buffer 504, input buffer 506 and input buffer 508 canbe assigned to OC10-11, OC22-23, OC36-37 and OC45-46, respectively. Infurther illustration in an embodiment, a single buffer can be assignedto all of the remaining OC frames. For example, input buffer 502 couldbe assigned to all of the OC frames not transporting TDM traffic (i.e.,OC10-11, OC22-23, OC36-37 and OC45-46). The above illustrations ofassignments of the OC frames to the different buffers is by way ofexample and not by way of limitation, as any size concatenation of OCframes across any of a number of locations in the SONET signal can be inany combination for assignment to input buffers 502-508 and outputbuffers 510-516.

Returning to FIGS. 3 and 4, physical connection circuitry 210 receivespacket data from optical and/or electrical lines coupled to inputbuffers 502-508. In an embodiment, the optical line and/or electricallines coupled to physical connection circuitry 210 are transmittingpacket data across a SONET-based signal. In one embodiment, this packetdata is being transmitted based on TDM. In an embodiment, the opticaland/or electrical lines coupled to input buffers 502-508 aretransporting the packet data using the Ethernet-based standard. In onesuch embodiment, the packet data is transmitted within the payload ofthe SONET frames. Moreover, a given packet, depending on its size, maybe stretched across more than one SONET frame.

Upon receipt of the packet data, physical connection circuitry 210 ofline card 302 places the packet data into one of input buffers 502-508.In an embodiment, physical connection circuitry 210 is programmed toplace the packet data from given STS SONET frames into one of inputbuffers 502-508. For example, if physical connection circuitry 210 iscoupled to an optical line transporting an OC-48 SONET signal, inputbuffer 502-508 could be assigned to receive OC1-4, OC5-11, OC40-48 andOC 25, respectively. Accordingly, the data in the payload of these SONETframes are placed into the associated buffers.

Moreover, physical connection circuitry 210 locates the packetboundaries within the packet data located in input buffers 502-508. Asdescribed above, a given packet may be stretched across a number ofSTS-1 SONET frames. Accordingly, a given packet is not necessarilycontained within a given STS-1 SONET frame. Therefore, physicalconnection circuitry 210 locates the boundaries between the packetsstored in input buffers 502-508, by determining the beginning and endingof the packets within input buffers 502-508. Techniques for locatingpacket boundaries for different protocols are known in the art. Forexample, for an ATM protocol, an ATM header and payload are of fixedsizes such that the ATM header can be identified based on a unique bitcombination, thereby allowing for the locating of the ATM packets.

Upon locating a packet boundary for a given packet, physical connectioncircuitry 210 forwards the packet to ingress packet processing circuitry212. In an embodiment, ingress packet processing circuitry 212 canperform mapping, possible multiple de-encapsulating and/or multipleencapsulating of different protocol headers of the given packet, whichis described in more detail in a patent application titled “A Method andApparatus for Switching Data of Different Protocols” to David Stiles,filed on Dec. 30, 2000, Serial No: Unassigned, Attorney Docket Number:004906.P002, which is hereby incorporated by reference.

Subsequent to any demapping, de-encapsulation and/or encapsulation,ingress packet processing circuitry 212 forwards the packets to egresspacket processing circuitry 214 of a different or same line card basedon the address for the given packet. In particular, a table stored inmemory within the given network element includes an association betweena given address and the destination line card number as well as a portnumber of a given buffer within physical connection circuitry 210 ofthis destination line card, which is described in more detail in apatent application titled “A Method and Apparatus for Switching Data ofDifferent Protocols” to David Stiles, filed on Dec. 30, 2000, Serial No:Unassigned, Attorney Docket Number: 004906.P002.

Returning to FIGS. 3 and 4, to help illustrate, ingress packetprocessing circuitry 212 of line card 302 forwards a packet to egresspacket processing circuitry 214 of line card 314 through packet mesh 226(not shown), as illustrated by the data path between line card 302 andline card 314. Moreover, assuming that this packet is destined foroutput buffer 510 within line card 314, the address for this particularpacket is associated with the number for line card 314 as well as theport number of output buffer 510, based on the table stored withinin-ring network element 102. In an embodiment, a proprietary protocol isemployed on packet mesh 226 for the transferring of packets between thedifferent line cards. In one such embodiment, the protocol allows forthe transfer of the port number of the given output buffer to which thepacket is destined within the line card to which such a packet is beingforwarded.

As described above, egress packet processing circuitry 214 includes amemory for the temporary storage of packets, which can be received fromvarious ingress packet processing circuitry 212 on different line cardswithin a given in-ring network element. For example, egress packetprocessing circuitry 214 of line card 314 can receive packets fromingress packet processing circuitry 212 from any of line cards 302-316.Upon receipt of packets, in an embodiment, egress packet processingcircuitry 214 can de-encapsulate and/or encapsulate the incoming packetswith protocol headers, which is described in more detail in a patentapplication titled “A Method and Apparatus for Switching Data ofDifferent Protocols” to David Stiles, filed on Dec. 30, 2000, Ser. No.______ Unassigned, Attorney Docket Number: 004906.P002. Additionally,egress packet processing circuitry 214 forwards these packets tophysical connection circuitry 210. Physical connection circuitry 210places a given packet into a given output buffer based on the portnumber of the buffer associated therewith. In an embodiment, aproprietary protocol allows for the transmitting of the port number ofthe buffer for a given packet between egress packet processing circuitry214 and physical connection circuitry 210.

As described above, a given output buffer can be provisioned to beassociated with one to a number of SONET frames within a TDM-based SONETsignal being transmitted among in-ring network elements 102-108. In onesuch embodiment, the number of SONET frames to be concatenated for agiven output buffer can be of any size. Moreover, in an embodiment, theconcatenated SONET frames can be located anywhere within the TDM-basedSONET signal, as illustrated by the SONET signal of FIG. 6. Physicalconnection circuitry 210 places the received packets located in outputbuffers 510-516 into the payload of SONET frames. Additionally, physicalconnection circuitry 210 places such SONET frames into the timeslotswithin the TDM-based SONET signal that are associated with the outputbuffer from which the packet was extracted. For example, output buffer510 could be associated with SONET frames OC1, OC5-10 and OC47-48 of aTDM-based SONET signal. Accordingly, packets located in output buffer510 can be placed into any of OC 1, OC5-10 and OC47-48 within theTDM-based SONET signal. Once the packet is transmitted within one of theparticular timeslots in the TDM-based SONET signal, this packet can bereceived by physical connection circuitry 210 of the line card in thenetwork element for which such a packet is destined.

Returning to FIGS. 3 and 4 to help illustrate, this given packet istransmitted from line card 314 of in-ring network element 102 to linecard 318 of in-ring network element 104 through the TDM-based SONETsignal being transported among in-ring network elements 102-108.Accordingly, this packet is received by physical connection circuitry210 of line card 318. The subsequent transmission of the packet deviatesbetween FIG. 3 and FIG. 4. Accordingly, the remaining transmission ofthe packet illustrated in FIG. 3 and FIG. 4 will now be describedseparately below.

With regard to the remaining transmission of the packet illustrated inFIG. 3, after receiving this given packet, physical connection circuitry210 of line card 318 places this packet into one of input buffers502-508, depending on which OC frames are associated with input buffers502-508, as described above. Moreover, because this given packet can becombined with other packet data being received from other sources,including from non-ring network elements, physical connection circuitry210 may need to relocate the packet boundaries for the packet datawithin input buffers 502-508, as described above. Once the packets areidentified, physical connection circuitry 210 forwards these packets toingress packet processing circuitry 212 of line card 318, as describedabove.

Upon receipt of packets, in an embodiment, ingress packet processingcircuitry 212 can map, de-encapsulate and/or encapsulate the incomingpackets with protocol headers, which is described in more detail in apatent application titled “A Method and Apparatus for Switching Data ofDifferent Protocols” to David Stiles, filed on Dec. 30, 2000, Ser. No.______ Unassigned, Attorney Docket Number: 004906.P002. Additionally,ingress packet processing circuitry 212 of line card 318 forwards thepacket to egress packet processing circuitry 214 of line card 328through packet mesh 226 (not shown), as illustrated by the data pathbetween line card 318 and line card 328. Moreover, assuming that thispacket is destined for output buffer 510 within line card 328, theaddress for this particular packet is associated with the number forline card 328 as well as the port number of output buffer 510, based onthe address stored in the tables located within in-ring network element104. In an embodiment, a proprietary protocol is employed on packet mesh226 for the transferring of packets between the different line cards. Inone such embodiment, the protocol allows for the transfer of the portnumber of the given output buffer to which the packet is destined withinthe line card to which such a packet is being forwarded.

Upon receipt of packets, in an embodiment, egress packet processingcircuitry 214 of line card 328 can de-encapsulate and/or encapsulate theincoming packets with protocol headers, which is described in moredetail in a patent application titled “A Method and Apparatus forSwitching Data of Different Protocols” to David Stiles, filed on Dec.30, 2000, Ser. No. ______ Unassigned, Attorney Docket Number:004906.P002. Moreover, egress packet processing circuitry 214 of linecard 328 forwards this packet to physical connection circuitry 210 ofline card 328. Physical connection circuitry 210 places a given packetinto a given output buffer based on the port number of the bufferassociated therewith. In an embodiment, a proprietary protocol allowsfor the transmitting of the port number of the buffer for a given packetbetween egress packet processing circuitry 214 and physical connectioncircuitry 210.

In contrast to the transmission of a packet between in-ring networkelements, this packet is being transmitted to a network element externalto network ring 114. Accordingly, for those packets being transmittedexternal to network ring 114 on a SONET-based signal, the standardsassociated with the SONET protocol, including Bellcore GR-253, must befollowed in order to communicate with SONET standard-based networkelements. Currently, such a standard does not allow for the number ofSTS frames within a SONET signal to be of any size of concatenation.Moreover, such a standard does not allow such concatenated STS frames tobe located anywhere within the SONET signal.

For example, under these current SONET standards, the base signal ofSTS-1 can be expanded to include 3 STS frames (STS-3) and multiples offour thereafter (e.g., STS-12, STS48 and STS-192). Moreover, under thecurrent SONET standard, a given set of STS frames are required to beequally interleaved (i.e., concatenated) within a given SONET signal.For example, if a given SONET signal includes 48 STS frames (i.e., anSTS-48 signal) and only 12 of the STS frames are currently carrying datatraffic (i.e., STS-12), these 12 STS frames are interleaved equallyacross the STS48 signal. Accordingly, every fourth STS frame istransmitting data traffic. In other words in contrast to in-ring networkelements 102-108 (network elements according to embodiments of thepresent invention), for those network elements that are limited tocarrying data traffic based on the SONET standard, the concatenation orinterleaving of a given set of STS frames could not be of any size, suchas STS-11, across any location, such as the first 11 STS frames.

Therefore, for those output buffers 510-516 within physical connectioncircuitry 210 of line card 328 that are transmitting packets to networkelements external to network ring 114 using a SONET signal, such buffersare programmed to place the packets into SONET standard-based locationswithin the SONET signal being transmitted to a non-ring network element.Returning to FIG. 3 to help illustrate, assuming that the packettransmission between in-ring network element 104 and non-ring networkelement 111 is SONET-based, output buffer 510 of line card 328 isassociated with SONET standard-based locations within such a signal. Forexample, if the SONET signal is OC-12 and output buffer 510 isassociated with OC-3, this packet within output buffer 510 could beplaced in the OC1, OC6 or OC12 locations.

Embodiments of the present invention were described in terms of a SONETsignal being transmitted between in-ring network element 104 andnon-ring network element 111. However, embodiments of the presentinvention are not so limited, as other types of data transmissionsignals can be employed. For example, if non-ring network element 111 isa router, this signal could be a packet-based stream.

Returning to FIG. 4 to describe the completion of the packettransmission therein, the given packet is located within physicalconnection circuitry 210 of line card 318. Describing the remainingpacket transmission of FIG. 4 generally, because the packet is beingrouted through at least three in-ring network elements within networkring 114, this given packet may remain in possibly any location of anyconcatenation within the TDM data stream because the packet is beingtransmitted between two in-ring network elements that can processpackets within these non-SONET based standard locations. Accordingly,the switch fabric of certain in-ring network elements may be employedfor the transmission of the packet inside network ring 114, instead ofpacket mesh 226 therein, as illustrated by the transmission of thepacket in FIG. 3.

In particular, this given packet that is located within at least one STSframe of the SONET signal, which is transmitted between in-ring networkelement 102 and 104, is transmitted through the switch fabric of in-ringnetwork element 104, as this packet remains in this STS frame of theTDM-based SONET signal between in-ring network elements 104 and 106.Physical connection circuitry 210 of line card 318, therefore, transmitsthis at least one STS frame containing the packet to TDM processingcircuitry 216 of line card 318. In turn, TDM processing circuitrytransmits this STS frame to control card 220 of line card 318. Controlcard 220 determines which outgoing line card within in-ring networkelement 104 that this STS frame is destined to be transmitted through,based on forwarding tables therein.

As shown by FIG. 4, control card(s) 342 transmits this STS frame to TDMprocessing circuitry 216 of line card 332. Accordingly, TDM processingcircuitry 216 receives and transmits this STS frame to physicalconnection circuitry 210 of line card 332. In turn, physical connectioncircuitry 210 of line card 332 transmits this STS frame to physicalconnection circuitry 210 of line card 408 within in-ring network element106. Therefore, this STS frame containing the packet is received byphysical connection circuitry 210 of line card 408. Moreover, becausethis packet is being transmitted to a network element external tonetwork ring 114 (i.e., non-ring network element 112), this packet willneed to be extracted from the STS frame. In particular, this packet willneed to be extracted from the STS frame because this STS frame may be ina set of concatenated frames of any size, which is not compliance withcurrent SONET standards, including Bellcore GR-253. Accordingly,physical connection circuitry 210 removes the packet from the STSframe(s) and buffers this data in one of input buffers 502-508 that isassigned to the STS frame(s), as described above.

Moreover, because this given packet can be combined with other packetdata being received from other sources, including from non-ring networkelements, physical connection circuitry 210 of line card 408 may need torelocate the packet boundaries for the packet data within input buffers502-508, as described above. Once the packets are identified, physicalconnection circuitry 210 forwards these packets to ingress packetprocessing circuitry 212 of line card 408, as described above.

Ingress packet processing circuitry 212 of line card 408 cande-encapsulate and/or encapsulate the incoming packets with protocolheaders, which is described in more detail in a patent applicationtitled “A Method and Apparatus for Switching Data of DifferentProtocols” to David Stiles, filed on Dec. 30, 2000, Ser. No. ______Unassigned, Attorney Docket Number: 004906.P002. Additionally, ingresspacket processing circuitry 212 of line card 408 forwards the packet toegress packet processing circuitry 214 of line card 414 through packetmesh 226 (not shown), as illustrated by the data path between line card408 and line card 414. Moreover, assuming that this packet is destinedfor output buffer 510 within line card 414, the address for thisparticular packet is associated with the number for line card 414 aswell as the port number of output buffer 510, based on the addressstored in the tables located within in-ring network element 106.

Upon receipt of this packet, egress packet processing circuitry 214 ofline card 414 forwards this packet to physical connection circuitry 210of line card 414. Physical connection circuitry 210 places a givenpacket into a given output buffer based on the port number of the bufferassociated therewith. In contrast to the transmission of a packetbetween in-ring network elements, this packet is being transmitted to anetwork element external to network ring 114. Accordingly, for thosepackets being transmitted external to network ring 114 on a SONET-basedsignal, the standards, including Bellcore GR-253, associated with theSONET protocol must be followed in order to communicate with SONETstandard-based network elements. As described above, currently, suchstandards do not allow for the number of STS frames within a SONETsignal to be of any size of concatenation. Moreover, such standards donot allow such concatenated STS frames to be located anywhere within theSONET signal.

Therefore, for those output buffers 510-516 within physical connectioncircuitry 210 of line card 414 that are transmitting packets to networkelements external to network ring 114 using a SONET signal, such buffersare programmed to place the packets into SONET standard-based locationswithin the SONET signal being transmitted to a non-ring network element.This packet is transmitted to non-ring network element 112. In anembodiment wherein the in-ring network element 106 and non-ring networkelement 112 are communicating through a SONET signal, this packet islocated within a SONET standard-based location within this SONET signal.

The embodiment of the packet transmission illustrated in FIG. 4 is byway of example and not by way of limitation, as other methods can beemployed in the routing of the packet across network ring 114. In onesuch embodiment, the data packet transmission internal to in-ringnetwork element 104 could be through the different packet processingcircuitry and packet mesh 226. For example, if a number of concatenatedSTS frames within a SONET signal being transmitted between two in-ringnetwork elements include more than one customer, the physical processingcircuitry in the line cards may need to remove the packets in theseconcatenated frames to allow different packets to be transmitted outsidenetwork ring 114 each time this concatenated frame enters an in-ringnetwork element.

Returning to FIG. 1 to help illustrate, assume packets from customer Aare being transmitted from non-ring network element 110 to non-ringnetwork element 112 through in-ring network elements 102-106. Assumealso that packets from customer B are being transmitted from non-ringnetwork element 110 to non-ring network element 111 through in-ringnetwork elements 102-104. Additionally, the packets from customer A andB share a concatenated set of STS frames in the SONET signal withinnetwork ring 114. Therefore, in each of in-ring network elements102-106, these packets would need to be removed from the STS frames todetermine whether the routing of such packets.

Accordingly, this filling of holes within the SONET signal provides amore efficient use of the bandwidth of the SONET signal. In particular,the SONET standard requires integer multiples of STS-1 (e.g., STS-3,STS-12 and STS48) for the interleaving of the multiple frames within aSONET signal, which causes holes within the SONET signal to be presentthat cannot be filled for a given set of customers. For example, ifSTS-2 worth of bandwidth remained in a given SONET signal and theminimum for a given customer is STS-3, this bandwidth is wasted.However, as shown, embodiments of the present invention fill the holesin the SONET signal with any size and location of packets.

The line cards and control cards included in the different networkelements include memories, processing elements and/or ApplicationSpecific Integrated Circuits (ASICs). Such memory includes amachine-readable medium on which is stored a set of instructions (i.e.,software) embodying any one, or all, of the methodologies describedherein. Software can reside, completely or at least partially, withinthis memory and/or within the processing elements and/or ASICs. For thepurposes of this specification, the term “machine-readable medium” shallbe taken to include any mechanism that provides (i.e., stores and/ortransmits) information in a form readable by a machine (e.g., acomputer). For example, a machine-readable medium includes read onlymemory (ROM); random access memory (RAM); magnetic disk storage media;optical storage media; flash memory devices; electrical, optical,acoustical or other form of propagated signals (e.g., carrier waves,infrared signals, digital signals, etc.); etc.

Thus, a method and apparatus for the incorporation of any size andlocation of concatenated SONET frames, which carry packet data, in aSONET signal have been described. Although the present invention hasbeen described with reference to specific exemplary embodiments, it willbe evident that various modifications and changes may be made to theseembodiments without departing from the broader spirit and scope of theinvention.

For example, the processing of the TDM and packet data were described interms of execution by multiple line cards and multiple processingelements (e.g., ingress packet processing circuitry 212). However,embodiments of the present invention are not so limited. For example, asingle line card could incorporate the processing described acrossmultiple line cards in the network elements. Moreover, a singleprocessing element could incorporate the processing described acrossmultiple processing elements.

To further illustrate possible modifications to embodiments of thepresent invention, the buffers shown within the different processingelements could be removed if the processing by the processing elementswas executing at such a rate that buffers were not required to hold thereceived data. Accordingly, the specification and drawings are to beregarded in an illustrative rather than a restrictive sense.

1. A method comprising: receiving packet data; concatenating the packetdata into a Time Division Multiplexing (TDM) Synchronous Optical Network(SONET) signal, wherein the concatenation can be across any locationswithin the TDM SONET signal and wherein a size of the concatenation canbe in increments of single SONET frames; and transmitting the TDM SONETsignal having the concatenated packet data.
 2. The method of claim 1,wherein the packet data is concatenated within locations in the TDMSONET signal not occupied by TDM data traffic.
 3. The method of claim 1,wherein the transmitting of the TDM SONET signal is between two networkelements in a network ring. 4-18. (canceled)
 19. A machine-readablemedium that provides instructions, which when executed by a machine,cause said machine to perform operations comprising: receiving packetdata; concatenating the packet data into a Time Division Multiplexing(TDM) Synchronous Optical Network (SONET) signal, wherein theconcatenation can be across any locations within the TDM SONET signaland wherein a size of the concatenation can be in increments of singleSONET frames; and transmitting the TDM SONET signal having theconcatenated packet data.
 20. The machine-readable medium of claim 19,wherein the packet data is concatenated within locations in the TDMSONET signal not occupied by TDM data traffic.
 21. The machine-readablemedium of claim 19, wherein the transmitting of the TDM SONET signal isbetween two network elements in a network ring. 22-27. (canceled)